The present invention relates to an agricultural working machine with a control unit for controlling and regulating at least one steering brake for selective braking of at least one of multiple, ground-engaging means of the agricultural working machine, for steering support and a method for implementing the control and regulating.
Agricultural working machines such as tractors, self-propelled harvesting machines, or earth-moving vehicles (without limitation), usually comprise multiple axles, wherein an axle for changing the direction of travel is equipped, for example, with steerable wheels and wherein a change in the direction of travel takes place along a turning circle specified by the steering of the wheels. For the purpose of deceleration, working machines comprise not only a service brake, which provides for a uniform deceleration in the direction of travel without lateral distortion, but also a so-called steering brake. This steering brake provides for a unilateral braking of a driven wheel such that, during off-road travel, it is possible to travel around curves that are narrower than the turning circle that is specified by the steerable wheels. For this purpose, in order to support the steering, the driven wheels on the side of the vehicle on the inside of the curve can be braked, while the wheels on the opposite side of the vehicle can continue to be driven without being braked.
In modern, and all-wheel drive, working machines having large tire dimensions on the front axle and improved ballasting of the front axles with a correspondingly effective steering-knuckle steering, the steering brake is usually used on muddy ground surfaces and when ballasting is unfavorable, in order to improve the steerability or to allow for particularly small turning clearance circles. This makes it possible, for example, at a headland, to travel through very small turning radii with the attached implement raised in the rear and with a correspondingly reduced load on the front axle.
Such steering brakes are known from DE 1 270 961 B and from EP 2 093 111 A1, wherein, in each case, a manual actuation of the steering brake is carried out by the operator of the working machine. EP 0 863 062 B12 makes known a brake system for increasing the driving safety for a tractor, which, in particular in the case of an all-wheel drive tractor, provides for an individual and side-specific control of the brakes in order to avoid a lockup of the wheels even under adverse conditions, which would overtax conventional antilock brake systems.
The disadvantage of steering brakes used nowadays is the need for manual actuation and the frequent dosing of the braking force. For this purpose, two brake pedals are usually provided, which brake pedals are disposed next to one another and can be actuated individually or jointly. The driver can be easily overtaxed, for example, at a headland, if a headland management system is unavailable, since the control of the attached implement is already consuming his full attention. In addition, the dosing of the braking force, in particular, in the case of power brakes, is not easy. As a rule, the rear axle is braked more strongly than would be necessary in order to achieve the steering angle set at the front axle. This results in an unsteady steering procedure and strain in the chassis elements.